Tuesday, September 9, 2008

Half Sigma has commented frequently on the downward trend of Republicans IQ as estimated by the WORDSUM variable in the General Social Survey (GSS).

While Half Sigma has identified the trend correctly, the numbers are presented in a somewhat misleading manner.His report looks at the raw numbers of scorers in each category and is therefore misleading because it doesn't reflect the proportion of people identifying with each party. Rearranging the numbers to reflect the percentage of people from each party falling into each category, we see a more accurate picture.

UPDATE: First, let's look at the average score from 1974 through 2010 and then we'll look at how the distribution has changed. This graph shows that the gap between Republicans, who tend to have higher IQ's and Democrats who tend to have lower IQ's has dropped on the GSS WordSum vocabulary test from 0.6 in 1974 to 0.3 in 2010. The top of the blue line shows the average Republican score and the average Democrat score. The independents who expressed a preference are grouped with the party they favor. And yes, I color the Republicans blue. I'm sick enough of the left stealing terms like "liberal" and trying to stick us with their soiled words ("fascist"). Are we really going to let them swap colors with us just because they've soiled the term "socialist" the color that goes along with it?

Democrat IQ deficit (blue area) has been slowly diminishing

Let's consider two questions: why has this gap changed, and what happens if we look at the distribution of scores.